This project is concerned with the maintenance and distribution of a cohesive and comprehensive database of information about restriction endonucleases and their associated methylases. REBASE has been in existence since 1975 and is currently implemented in a relational format under Sybase. Information enters the database both from the published literature or by direct submission from the investigators either prior to publication or instead of publication. Approximately two thirds of the present entries are unpublished other than through REBASE. The information is disseminated throughout the world both by formal publication in the scientific literature and in a variety of electronic formats. Thus monthly updates are posted and selected files distributed through an automatic E- mail list to about 125 sites. In addition, the information is available by anonymous FTP or through WAIS. Additional distribution mechanisms are proposed including through World Wide Web. Among the files maintained and updated monthly are specialized ones that are used by some of the more widely used computer programs, such as GCG and Intelligenetics. These files are ready to use and include up to date information about the full range of specificities and their commercial availability. The information available through REBASE is key to all investigators planning experiments to cleave and/or religate DNA. It is a unique resource for the practice of Biotechnology and its contents are used directly or indirectly by many sections of the Research Health Care Community.